BMW and 2nd hand bikes

Anybody who is thinking about buying a 2nd hand BMW bike should think twice. Not sure if the same applies whether you buy it from a BMW dealership or another bike shop but this is my experience which I find very unfair and not very customer friendly. Always loved BMW's (had 5 BMW's in my lifetime...now am having 2nd thoughts). My BMW R1200RS nav VI was giving problems so took it to Fire It Up (from whom I bought it) they said, can't help need to take it to BMW. Took it to BMW Cedar Isle (very bad customer service, during the month and 2 weeks they had it, I had to call them every time for an update, they never gave feedback on what was happening unless I asked, very poor service). I also informed them that I was going on tour on 21st Sept and needed it fixed. Long story short at the last minute on the Friday before I left (after a month and 2 weeks) BMW Cedar Isle inform me ".....sorry can't help you as BMW SA want original invoice of purchase before they will replace navigation (as it was system problem and had to be replaced). Now I ask you with tears in my eyes, how is somebody who buys a 2nd hand car/bike supposed to produce the original invoice, surely BMW will have this on their system it is all linked to the bike VIN and chassis number etc....So anybody wanting to but a 2nd hand BMW bike, be careful you will be left in the lurch should something go wrong. Still waiting for somebody from BMW customer care to contact me...customer care is an oxy***** when it comes to BMW it seems. Very unfair.